Systems, methods and devices for cellular synchronization references

ABSTRACT

Cellular (e.g., LTE or UMTS) and global navigation satellite system (GNSS) based technologies can provide ubiquitous and seamless synchronization solution for LTE-based vehicle to everything (V2X) or Proximity Services synchronization (ProSe) services. For example, by using joint GNSS timing references and LTE cellular network timing references for V2X or ProSe system synchronization benefits of using GNSS technologies to improve synchronization procedure for LTE based V2X or ProSe services can be enabled, including: (1) accurate and stable timing, (2) availability of a global and stable timing reference and (3) ability to propagate GNSS timing by user equipment having sufficient GNSS signal quality.

RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 62/232,371 filed Sep. 24, 2015, which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to cellular timing references and morespecifically to selecting and prioritizing cellular timing referencesfrom network references, global navigation satellite system referencesand propagated references.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a navigation reference systemconsistent with embodiments disclosed herein.

FIG. 2 is a diagram illustrating a long term evolution (LTE)communication frame consistent with embodiments disclosed herein.

FIG. 3 is a diagram illustrating multiple timing references provided toa user equipment (UE) consistent with embodiments disclosed herein.

FIG. 4 is a diagram illustrating propagation of timing referencesconsistent with embodiments disclosed herein.

FIG. 5 is a diagram of synchronization resource timing consistent withembodiments disclosed herein.

FIG. 6 is a block diagram illustrating electronic device circuitryconsistent with embodiments disclosed herein.

FIG. 7 is a diagram of a UE consistent with embodiments disclosedherein.

FIG. 8 is a flow chart illustrating a method for prioritizing an LTEtiming reference consistent with embodiments disclosed herein.

FIG. 9 is a diagram illustrating a computing system consistent withembodiments disclosed herein.

DETAILED DESCRIPTION

A detailed description of systems and methods consistent withembodiments of the present disclosure is provided below. While severalembodiments are described, it should be understood that the disclosureis not limited to any one embodiment, but instead encompasses numerousalternatives, modifications, and equivalents. In addition, whilenumerous specific details are set forth in the following description inorder to provide a thorough understanding of the embodiments disclosedherein, some embodiments can be practiced without some or all of thesedetails. Moreover, for the purpose of clarity, certain technicalmaterial that is known in the related art has not been described indetail in order to avoid unnecessarily obscuring the disclosure.

Techniques, apparatus and methods are disclosed that enable cellular(e.g., LTE or UMTS) and GNSS based technologies to provide ubiquitousand seamless synchronization solution for LTE-basedvehicle-to-everything (V2X) services. For example, by using joint GNSStiming references and LTE cellular network timing references for V2Xsystem synchronization (or Proximity Services synchronization (ProSe))benefits of using GNSS technologies to improve synchronization procedurefor LTE based V2X services can be enabled, including: (1) accurate andstable timing, (2) availability of a global and stable timing referenceand (3) ability to propagate GNSS timing by UE terminals havingsufficient GNSS signal quality.

It should be noted that when V2X is described, the embodiment can alsoapply to LTE proximity services (ProSe).

In an example of (1), accurate and stable timing provided by GNSSsystems can be used to discipline local oscillators of LTE based V2Xterminals (or ProSe terminals) resulting in carrier frequency closer toabsolute carrier frequency value and reduce deviation of carrierfrequency offset between terminals. Options to enable the timingreferences include: A) new technical specifications can be defined onfrequency offset and stability for V2X terminals equipped with GNSSreceivers and/or utilizing GNSS to discipline local oscillators; and/orB) define new specifications on frequency offset for V2X capableterminals without mandating how it is achieved.

In an example of (2), availability of a global and stable timingreference (at least in free space environments when there is no blockageof signal from satellites) can significantly simplify synchronizationprocedure for V2X operation. For example, synchronization with a networkreference, a propagated reference or a GNSS reference would result in asimilar timing reference signal.

In an example of (3), GNSS timing can be propagated by UE terminalshaving sufficient GNSS signal quality (e.g., to a global synchronizationreference). In this example, the GNSS signal quality may be defined suchthat V2X terminal using GNSS for synchronization (e.g., to discipline alocal oscillator) to have accurate synchronization and thus maypropagate its own timing. Optionally, instead of defining the GNSSsignal quality, the synchronization quality may be defined.

Wireless mobile communication technology uses various standards andprotocols to transmit data between a base station and a wireless mobiledevice. Wireless communication system standards and protocols caninclude the 3rd Generation Partnership Project (3GPP) long termevolution (LTE); the Institute of Electrical and Electronics Engineers(IEEE) 802.16 standard, which is commonly known to industry groups asworldwide interoperability for microwave access (WiMAX); and the IEEE802.11 standard, which is commonly known to industry groups as Wi-Fi. In3GPP radio access networks (RANs) in LTE systems, the base station caninclude Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs,eNodeBs, or eNBs) and/or Radio Network Controllers (RNCs) in an E-UTRAN,which communicate with a wireless communication device, known as userequipment (UE). The UE uses a radio access technology (RAT) to connectto a RAN.

Vehicular communication is a relatively new but rapidly emergingresearch and development area of wireless communication systems. Thereis a quite diverse set of applications that can be enabled byIntelligent Transportation Systems (ITS), if wireless technologies areutilized. The range of applications varies from road safety andvehicular traffic management to the applications enabling the vision of“connected car”, infotainment and “autonomous driving”. The variousexisting applications and use cases are characterized by very diversespecifications and/or technical boundaries, which can be challenging tosatisfy. Moreover, in order to meet these specifications and/ortechnical boundaries different principles of operation/communication canbe applied. The broad range of vehicular system specifications and/ortechnical boundaries includes multiple challenges associated with thereal-time packet delivery (latency), reliability of packet delivery,seamless connectivity and ubiquitous coverage. Besides mandated systemspecifications and/or technical boundaries, there can be additionaltechnical obstacles associated with the system synchronization, channelpropagation conditions (high Doppler), mobility and operation in denseenvironments. These factors can use a combination of differentcommunication principles to enable efficient support of diverse V2Xservices.

Recently, the 3GPP initiated study on enhancements of LTE technology tosupport V2X services. The LTE system may provide a unique advantage forvarious V2X services, since the technology is being deployed worldwideand thus can provide the ubiquitous coverage and connectivity to V2Xapplications. In addition, in LTE R.12 the D2D communication anddiscovery frameworks were integrated enabling direct communication anddiscovery between UEs. These sidelink frameworks in combination with thetraditional cellular LTE operation and assistance from the network sidemay provide superior performance characteristics in terms of V2Xreliability, latency and capacity. However, there are still quite manychallenges that can be resolved. One of the main problems that can usean additional enhancement to enable LTE-based V2X solutions is areliable and accurate synchronization. The LTE Release 12 sidelinksynchronization procedure (defined for sidelink communication anddiscovery) may be not sufficient and can use additional modifications inorder to use LTE sidelink air-interface for V2X services, especially inout of coverage scenarios. In particular, the synchronization principlesdefined for sidelink communication in out of coverage rely on timingpropagation by a UE serving as a synchronizations source. In applicationto mobile V2X environment, the UE based propagation may lead tosynchronization convergence issues and frequent re-synchronizationprocedures reflected in multiple asynchronous areas that may vary intime and space. This may result in unstable system behavior and lowperformance. In addition, the frequency accuracy and stability of UEoscillators may not be appropriate that will further complicatesynchronization process.

Therefore, in order to enable synchronous V2X operation within and outof network coverage scenarios the additional external synchronizationsources such as global navigation satellite systems (GNSS) can be usedfor synchronization in wide deployment areas.

LTE can be enhanced from synchronization perspective to utilize asidelink air-interface for V2X operation in multiple scenarios. Forexample, design enhancements can include GNSS based solutions that areapplied for LTE based V2X operation.

The basic principle of some embodiments is to use joint cellular (e.g.,LTE or UMTS) and GNSS based technologies to provide ubiquitous andseamless synchronization solution for LTE-based V2X services. Inparticular, we suggest enhancements that should be introduced to LTEsidelink synchronization framework/specification in order to use it forvehicle-to-vehicle (V2V) and V2X communication. An example of suchsystem architecture is shown in FIG. 1.

FIG. 1 shows a target device 102 (e.g., a UE or vehicle) equipped with aGNSS receiver and LTE transceiver. The target device 102 receives GNSSreference signals from GNSS reference sources 104 (e.g., GPS systemsignals, GLONASS system signals, other GNSS satellites, etc.). Thetarget device 102 also receives LTE radio signals for synchronizationassistance from the network (e.g., an eNB, etc.) by a network reference106. A V2X server 108 can also provide assistance information to thetarget device. The V2X server 108 can also provide assistanceinformation and geocasting and control parameters for V2X operation tothe network reference source 106 (e.g., the eNB). The V2X server 108 canreceive measurements (including location, speed, congestion reports,amount of vehicles, etc.) from the target device.

Wide area and seamless synchronization can be enabled in multipledeployment scenarios, including, in network coverage, partial networkcoverage and out of network coverage. Additional design enhancements andsignaling can be defined for V2X applications to enable thissynchronization. These enhancements can include (1) information aboutnetwork (eNBs) and GNSS synchronization status and timing offsetinformation; (2) indication of the alignment of network and GNSS timingto a common global timing reference; and/or (3) GNSS assistanceinformation for V2X terminals.

Enhancement (1) can include information about network (eNBs) and GNSSsynchronization status and timing offset information. This status andtiming information can include: a level of synchronization in phase,frequency, and/or time; and/or signaling of the timing offset in thegranularity of less that cyclic prefix (CP) duration (e.g., 1microsecond or below) relative to UTC time.

Enhancement (2) can include an indication of the alignment of networkand GNSS timing to a common global timing reference (e.g., UTC at leastwithin a very large geographical area) and alignment of resourceallocation within and out of network coverage to the global timingreference and absolute time.

Enhancement (3) can include GNSS assistance information for V2Xterminals. The GNSS assistance information can be broadcasted by theeNBs in system information blocks (SIB) or in any other broadcast,groupcast, and/or unicast channels. The GNSS assistance informationdefined in LTE positioning protocol (LPP) protocols can be reused (atleast partial content of 3GPP Assistance) to facilitate synchronizationand location services for V2X applications. An example set of data isshown below:

GNSS-CommonAssistData ::= SEQUENCE { GNSS-ReferenceTimeGNSS-ReferenceLocation GNSS-IonosphericModelGNSS-EarthOrientationParameters }

GNSS-ReferenceTime can be used with GNSS specific system time withuncertainty and the relationship between GNSS system time and networkair-interface timing of the eNodeB/NodeB/BTS transmission in thereference cell. An example set of data is shown below:

GNSS-ReferenceTime ::= SEQUENCE { GNSS-SystemTime,GNSS-ReferenceTimeForOneCell } GNSS-SystemTime ::= SEQUENCE {gnss-TimeID GNSS-ID, gnss-DayNumber INTEGER (0..32767), gnss-TimeOfDayINTEGER (0..86399), gnss-TimeOfDayFrac-msec INTEGER (0..999)notificationOfLeapSecond BIT STRING (SIZE(2)) gps-TOW-AssistGPS-TOW-Assist ... } GNSS-ReferenceTimeForOneCell ::= SEQUENCE {networkTime NetworkTime, referenceTimeUnc INTEGER (0..127), bsAlignENUMERATED {true} OPTIONAL, ... }

GNSS-ReferenceLocation can be used to provide the target device with apriori knowledge of its location in order to improve GNSS receiverperformance.

Other generic information elements may be provided by eNB to improveGNSS performance as captured in GNSS-GenericAssistDataElement andcorresponding subfields. An example set of data is shown below:

GNSS-GenericAssistDataElement ::= SEQUENCE { GNSS-ID, SBAS-ID CondGNSS-ID-SBAS GNSS-TimeModelList GNSS-DifferentialCorrectionsGNSS-NavigationModel GNSS-RealTimeIntegrity GNSS -DataBitAsistanceGNSS-AcquisitionAssistance GNSS-Almanac GNSS-UTC-ModelGNSS-AuxiliaryInformation }

Potential challenges associated with usage of GNSS technologies toimprove synchronization procedure for LTE based V2X services can beresolved or reduced, including power consumption and blockage of GNSSsignals. For example, the use of GNSS capable receivers can result insignificant power consumption. However, the power consumption might notbe an important design factor for terminals integrated to a vehicle and,in some embodiments, if GNSS is used for the purpose of synchronization,the power consumption may be reduced. In another example, when blockageof a GNSS signal occurs, the synchronization reference can be providedby the network or UEs having stable GNSS synchronization reference.

An integration of GNSS based synchronization option can increase theamount of available synchronization references. In one embodiment, botheNBs and UEs can provide synchronization reference to the UEs.Predefined rules are defined for selection of synchronization referenceby a device-to-device (D2D) transmitter. In the embodiment, an eNB hashigher priority as a synchronization reference, followed by a UEpropagating timing from eNB. The UE serving as an autonomoussynchronization reference has lower priority comparing to UEs(synchronization sources) propagating network timing and eNB.

An integration of GNSS based technology can introduce additional typesof synchronization sources, including (1) GNSS based synchronization,(2) network based synchronization and (3) UE based synchronization. InGNSS based synchronization, the GNSS technology itself can serve as aglobal timing reference for synchronization in phase, frequency and/ortime. In one embodiment, the eNB can provide a complementarysynchronization source and perform control functions by associating V2Xspectrum resources with global timing reference relative and networktransmission time. For example, a system frame number (SFN) can bemapped to UTC time with the finer time offset (e.g., an offset less than1 ms) being separately indicated.

In network based synchronization, eNBs are synchronized with GNSS infrequency, phase and/or time (eNB_(GNSS)). In one embodiment, an eNB canserve as a synchronization source for in-coverage scenarios. In thisembodiment, a timing relation between eNB transmission timing and globalV2X system time can be indicated to a UE in the particular geographicalarea. When the eNBs are not synchronized with GNSS, the eNBs might notuse GNSS synchronization but can provide a stable timing reference. Inasynchronous networks, the eNBs transmission timing might not besynchronized in phase and time, can be sufficiently accurate in terms offrequency synchronization.

In UE based synchronization, UEs can derive and/or propagatesynchronization timing from eNBs (UE_(SS-eNB)). These propagating UEscan propagate network timing references in case of partial coveragescenarios to enable receiving UEs (such as vehicle terminals) to haveproper synchronization when the receiving UEs approach the network fromout of coverage. The UEs can also derive and propagate synchronizationfrom GNSS (UE_(SS-GNSS)). A UE equipped with GNSS can have bettersynchronization accuracy in time and frequency, which can enable the UEto serve as a good synchronization reference. In an embodiment whereGNSS timing is used for V2X system and/or services, this UE canpropagate timing information towards other V2X users without availableGNSS sync (e.g., due to damage of GNSS module, blocked GNSS signals(e.g., in tunnel), etc.)

A UE can serve as an independent synchronization source (UE_(SS)). Anindependent synchronization source (i.e., that does not derive itstiming from any other synchronization reference sources except its ownlocal oscillator) can establish a synchronous operation in out ofcoverage scenarios. In some embodiments using V2X services, benefits ofusing such sources might be limited, resulting in a lowest priority orlower priority when compared with other synchronization references inLTE.

FIG. 2 is a schematic diagram 200 illustrating long term evolution (LTE)communication frame 204 of 10 ms duration 202. In one embodiment, eachfrequency allocation (carrier) can be in 180 kHz increments. In thediagram shown, a minimum of six carriers are shown. This allows for abandwidth of 1.08 MHz (six carriers times 180 kHz=1.08 MHz bandwidth).In some embodiments, the carriers can be expanded to 110 blocks (110carriers times 180 kHz=19.8 MHz). Frame 204 can be 10 ms with each slot208 being 0.5 ms (and each subframe 206 being 1 ms).

Slot 208 at a carrier is resource block 210, which includes sevensymbols at 12 orthogonal frequency-division multiplexing (OFDM)subcarriers. Resource element 212 is one OFDM subcarrier for theduration of one OFDM symbol. Resource block 210 can include 84 resourceelements 212 when using a normal cyclic prefix (CP). OFDM spacingbetween individual subcarriers in LTE can be 15 kHz. A guard period of aCP can be used in the time domain to help prevent multipath inter-symbolinterference (ISI) between subcarriers. The CP can be a guard periodbefore each OFDM symbol in each subcarrier to prevent ISI (such as dueto multipath).

FIG. 3 is a diagram illustrating multiple timing references provided toa user equipment (UE) consistent with embodiments disclosed herein. A UE302 receives synchronization timing references from GNSS referencesources 304 and network reference source 306. With both synchronizationtiming references available, the UE can determine and/or select asynchronization timing reference based on a determined priority. Thedetermined priority can be pre-determined, provided by the networkand/or dynamically determined.

In some embodiments, with an increased number of possiblesynchronization reference types, priority rules for synchronizationsource selection can be pre-defined (e.g., default priority rulesincluding parameters defining timing relations and their associationwith spectrum resource allocation). Alternatively, these rules can beprovided/configured by the network, if available, for each V2X systemcarrier.

For instance, the following general rules can be configured:

GNSS>eNB>UE_({GNSS, eNB}). This rule indicates that a GNSSsynchronization source has a highest priority as a synchronizationreference. The next priority is an eNB, and then a UE (deriving timingfrom an eNB or a GNSS).

eNB>GNSS>UE_({GNSS, eNB})>UE_(ISS). This rule indicates that the networkreference (e.g., an eNB) has a highest priority than synchronizationreference, followed by GNSS which is followed by a UE (deriving timingfrom eNB or GNSS), which is followed by a UE acting as an independentsynchronization source (ISS).

eNB>UE_({GNSS, eNB})>GNSS>UE_(ISS). This rule indicates that the networkreference (e.g., an eNB) has a highest priority as a synchronizationreference followed by a UE (deriving timing from eNB or GNSS), which isfollowed by GNSS, which is followed by a UE acting as an independentsynchronization source (ISS).

GNSS>UE_({GNSS, eNB})>eNB>UE_(ISS). This rule indicates that a GNSSsynchronization source has higher priority as a synchronizationreference followed by a UE (deriving timing from GNSS), which isfollowed by an eNB, which is followed by a UE acting as an independentsynchronization source (ISS).

Other combinations of priority rules for synchronization sourceselection can be defined. In some embodiments, an eNB and a GNSS can bejointly used for synchronization. These rules can be predefined byspecification or configured by network.

FIG. 4 is a diagram illustrating propagation of timing references, whichincludes out-of-coverage and partial coverage scenarios. In the exampleshown, UE_(eNB) 402 receives a synchronization reference signal from theeNB 406. UE_(eNB) propagates the synchronization information topartial-coverage UE 412 and out-of-coverage UE 410. UE 412 selects theonly synchronization reference available, which is the referenceprovided by source UE_(eNB) 402. UE_(GNSS) 408 receives a GNSS timingreference signal from GNSS system 404 (e.g., satellite, terrestrialantenna, etc.). UE_(GNSS) is out-of-coverage, as it does not havenetwork connectivity. UE_(GNSS) selects the GNSS synchronization sourceas the timing reference. UE_(GNSS) propagates the timing reference to UE410. UE 410, based on priority rules, selects the timing referenceprovided by UE_(GNSS), as having a higher priority than UE_(eNB).

In out of coverage scenarios, the following priority rules forsynchronization reference selection can be used:

GNSS>UE_(GNSS)>UE_(ISS). This rule indicates that the GNSSsynchronization source has a highest priority as a synchronizationreference followed by a UE deriving timing from the GNSS, which isfollowed by a UE acting as an independent synchronization source.

In a partial coverage scenario (when an eNB is not available butsynchronization source UE_({eNB}) is detected propagating timing fromthe network), the following priority rules for synchronizationreferences or sources can be defined:

GNSS>UE_(GNSS)>UE_(eNB)>UE_(ISS)

GNSS>UE_(eNB)>UE_(GNSS)>UE_(ISS)

UE_(eNB)>GNSS>UE_(GNSS)>UE_(ISS)

FIG. 5 is a diagram of synchronization resource timing, includingpropagation of synchronization reference by different types ofsynchronization sources. In some embodiments, synchronization signals orphysical sidelink broadcast channel (PSBCH) payloads can indicate asynchronization source (or reference). Timing information in LTE canalso be made implicit based on a relative timing of the signal. Forexample, timing reference signals 504 with a first offset 502 fromsystem frame number 0 (SFN0) or from a subframe boundary can be impliedto be from an eNB or an in-coverage UE. Timing reference signals 508with a second offset 506 from system frame number 0 (SFN0) or from asubframe boundary can be implied to be from a GNSS. While the signalshave different placement, the timing reference signals 504, 508 can havea period 510, over which the timing information repeats. In theembodiment shown, the period 510 is longer than an LTE frame 512.

In order to propagate synchronization timing, synchronization sourcescan transmit using synchronization channels and signals. In oneembodiment using LTE, PSBCH (physical sidelink broadcast channel),primary sidelink synchronization signals (PSSS) and/or secondarysidelink synchronization signals (SSSS) can be used. However, differentsynchronization sources (or references) can have differentsynchronization accuracy in frequency, phase and/or time. Todifferentiate the synchronization sources by type, dedicatedsynchronization resources, channels and/or signals can be allocated foreach type of synchronization source. For example, distinct sidelinksynchronization signal (SLSS) IDs and/or separate synchronizationresources can be assigned to synchronization sources deriving timingfrom eNB (UE_(eNB)), GNSS (UE_(GNSS)), GNSS+eNB (UE_(GNSS,+eNB)) orUE_(ISS).

An indication of the synchronization reference can be indicated usingdifferent methods, including carried by PSSS/SSSS signals, a PSBCHpayload and/or implicit indication. When carried by PSSS/SSSS signals,different subsets of existing sequences can be allocated for differentsynchronization reference types. For example, an additional PSSS rootindex for UEs deriving timing from GNSS can be defined. In anotherexample, new signals can be defined or a physical structure can bechanged, etc.

When a PSBCH payload is used, additional reserved fields can be added toexisting PSBCH content to indicate that timing is derived or propagatedfrom a timing reference, such as GNSS. The PSBCH payload can also carrycontent providing information on timing relation between GNSS systemtime, network transmission time and/or V2X system time.

In other embodiments, an implicit indication based on the time instanceof the synchronization resource relative to global time or SFN0 can beused, as shown in FIG. 5 and described above.

In some embodiments, when GNSS is used as a synchronization reference,an absolute time can be used to define a spectrum resources andtime-slotted structure for transmission. The timing can be accuratewithin the range of less than 1 microsecond (e.g., 100 nanoseconds).This sub-microsecond accuracy provides additional benefit of using GNSSas a reference, when compared to a timing derived from eNB, which doesnot compensate a propagation delay (i.e. utilize DL reception timing).In some embodiments, separate synchronization resources are allocatedthat can be used for transmission of synchronization signals by vehiclesthat are synchronized in absolute time.

UEs that propagate timing from an eNB can further adjust itstransmission timing in order to coarsely compensate the propagationdelay from eNB based on analysis of earliest signal arrival time. Forexample, the UE can compare signal reception timing from an eNB or froma UE propagating timing reference from GNSS or directly with GNSStiming. Adjustments can be configured and/or enabled by an eNB.

FIG. 6 is a block diagram illustrating electronic device circuitry 600that may be eNB circuitry, UE circuitry, network node circuitry, or someother type of circuitry in accordance with various embodiments. Inembodiments, the electronic device circuitry 600 may be, or may beincorporated into or otherwise a part of, an eNB, a UE, a mobile station(MS), a BTS, a network node, or some other type of electronic device. Inembodiments, the electronic device circuitry 600 may include radiotransmit circuitry 610 and receive circuitry 612 coupled to controlcircuitry 614. In embodiments, the transmit circuitry 610 and/or receivecircuitry 612 may be elements or modules of transceiver circuitry, asshown. The electronic device circuitry 610 may be coupled with one ormore plurality of antenna elements 616 of one or more antennas. Theelectronic device circuitry 600 and/or the components of the electronicdevice circuitry 600 may be configured to perform operations similar tothose described elsewhere in this disclosure.

In embodiments where the electronic device circuitry 600 is or isincorporated into or otherwise part of a UE, the transmit circuitry 610can transmit timing references as shown in FIG. 1. The receive circuitry612 can receive timing references as shown in FIG. 1.

In embodiments where the electronic device circuitry 600 is an eNB, BTSand/or a network node, or is incorporated into or is otherwise part ofan eNB, BTS and/or a network node, the transmit circuitry 610 cantransmit timing references as shown in FIG. 1. The receive circuitry 612can receive transmissions from the UE or timing references from the GNSSas shown in FIG. 1.

In certain embodiments, the electronic device circuitry 600 shown inFIG. 6 is operable to perform one or more methods, such as the methodsshown in FIG. 8.

As used herein, the term “circuitry” may refer to, be part of, orinclude an Application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group), and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablehardware components that provide the described functionality. In someembodiments, the circuitry may be implemented in, or functionsassociated with the circuitry may be implemented by, one or moresoftware or firmware modules. In some embodiments, circuitry may includelogic, at least partially operable in hardware.

Embodiments described herein may be implemented into a system using anysuitably configured hardware and/or software. FIG. 7 is a block diagramillustrating, for one embodiment, example components of a user equipment(UE) or mobile station (MS) device 700. In some embodiments, the UEdevice 700 may include application circuitry 702, baseband circuitry704, Radio Frequency (RF) circuitry 706, front-end module (FEM)circuitry 708, and one or more antennas 710, coupled together at leastas shown in FIG. 7.

The application circuitry 702 may include one or more applicationprocessors. By way of non-limiting example, the application circuitry702 may include one or more single-core or multi-core processors. Theprocessor(s) may include any combination of general-purpose processorsand dedicated processors (e.g., graphics processors, applicationprocessors, etc.). The processor(s) may be operably coupled and/orinclude memory/storage, and may be configured to execute instructionsstored in the memory/storage to enable various applications and/oroperating systems to run on the system.

By way of non-limiting example, the baseband circuitry 704 may includeone or more single-core or multi-core processors. The baseband circuitry704 may include one or more baseband processors and/or control logic.The baseband circuitry 704 may be configured to process baseband signalsreceived from a receive signal path of the RF circuitry 706. Thebaseband 704 may also be configured to generate baseband signals for atransmit signal path of the RF circuitry 706. The baseband processingcircuitry 704 may interface with the application circuitry 702 forgeneration and processing of the baseband signals, and for controllingoperations of the RF circuitry 706.

By way of non-limiting example, the baseband circuitry 704 may includeat least one of a second generation (2G) baseband processor 704A, athird generation (3G) baseband processor 704B, a fourth generation (4G)baseband processor 704C, other baseband processor(s) 704D for otherexisting generations, and generations in development or to be developedin the future (e.g., fifth generation (5G), 6G, etc.). The basebandcircuitry 704 (e.g., at least one of baseband processors 704A-704D) mayhandle various radio control functions that enable communication withone or more radio networks via the RF circuitry 706. By way ofnon-limiting example, the radio control functions may include signalmodulation/demodulation, encoding/decoding, radio frequency shifting,other functions, and combinations thereof. In some embodiments,modulation/demodulation circuitry of the baseband circuitry 704 may beprogrammed to perform Fast-Fourier Transform (FFT), precoding,constellation mapping/demapping functions, other functions, andcombinations thereof. In some embodiments, encoding/decoding circuitryof the baseband circuitry 704 may be programmed to perform convolutions,tail-biting convolutions, turbo, Viterbi, Low Density Parity Check(LDPC) encoder/decoder functions, other functions, and combinationsthereof. Embodiments of modulation/demodulation and encoder/decoderfunctions are not limited to these examples, and may include othersuitable functions.

In some embodiments, the baseband circuitry 704 may include elements ofa protocol stack. By way of non-limiting example, elements of an evolveduniversal terrestrial radio access network (EUTRAN) protocol including,for example, physical (PHY), media access control (MAC), radio linkcontrol (RLC), packet data convergence protocol (PDCP), and/or radioresource control (RRC) elements. A central processing unit (CPU) 704E ofthe baseband circuitry 704 may be programmed to run elements of theprotocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRClayers. In some embodiments, the baseband circuitry 704 may include oneor more audio digital signal processor(s) (DSP) 704F. The audio DSP(s)704F may include elements for compression/decompression and echocancellation. The audio DSP(s) 704F may also include other suitableprocessing elements.

The baseband circuitry 704 may further include memory/storage 704G. Thememory/storage 704G may include data and/or instructions for operationsperformed by the processors of the baseband circuitry 704 storedthereon. In some embodiments, the memory/storage 704G may include anycombination of suitable volatile memory and/or non-volatile memory. Thememory/storage 704G may also include any combination of various levelsof memory/storage including, but not limited to, read-only memory (ROM)having embedded software instructions (e.g., firmware), random accessmemory (e.g., dynamic random access memory (DRAM)), cache, buffers, etc.In some embodiments, the memory/storage 704G may be shared among thevarious processors or dedicated to particular processors.

Components of the baseband circuitry 704 may be suitably combined in asingle chip, a single chipset, or disposed on a same circuit board insome embodiments. In some embodiments, some or all of the constituentcomponents of the baseband circuitry 704 and the application circuitry702 may be implemented together, such as, for example, on a system on achip (SOC).

In some embodiments, the baseband circuitry 704 may provide forcommunication compatible with one or more radio technologies. Forexample, in some embodiments, the baseband circuitry 704 may supportcommunication with an evolved universal terrestrial radio access network(EUTRAN) and/or other wireless metropolitan area networks (WMAN), awireless local area network (WLAN) and/or a wireless personal areanetwork (WPAN). Embodiments in which the baseband circuitry 704 isconfigured to support radio communications of more than one wirelessprotocol may be referred to as multi-mode baseband circuitry.

The RF circuitry 706 may enable communication with wireless networksusing modulated electromagnetic radiation through a non-solid medium. Invarious embodiments, the RF circuitry 706 may include switches, filters,amplifiers, etc. to facilitate the communication with the wirelessnetwork. The RF circuitry 706 may include a receive signal path whichmay include circuitry to down-convert RF signals received from the FEMcircuitry 708, and provide baseband signals to the baseband circuitry704. The RF circuitry 706 may also include a transmit signal path whichmay include circuitry to up-convert baseband signals provided by thebaseband circuitry 704, and provide RF output signals to the FEMcircuitry 708 for transmission.

In some embodiments, the RF circuitry 706 may include a receive signalpath and a transmit signal path. The receive signal path of the RFcircuitry 706 may include mixer circuitry 706A, amplifier circuitry706B, and filter circuitry 706C. The transmit signal path of the RFcircuitry 706 may include filter circuitry 706C and mixer circuitry706A. The RF circuitry 706 may further include synthesizer circuitry706D configured to synthesize a frequency for use by the mixer circuitry706A of the receive signal path and the transmit signal path. In someembodiments, the mixer circuitry 706A of the receive signal path may beconfigured to down-convert RF signals received from the FEM circuitry708 based on the synthesized frequency provided by synthesizer circuitry706D. The amplifier circuitry 706B may be configured to amplify thedown-converted signals.

The filter circuitry 706C may include a low-pass filter (LPF) orband-pass filter (BPF) configured to remove unwanted signals from thedown-converted signals to generate output baseband signals. Outputbaseband signals may be provided to the baseband circuitry 704 forfurther processing. In some embodiments, the output baseband signals mayinclude zero-frequency baseband signals, although this is not arequirement. In some embodiments, the mixer circuitry 706A of thereceive signal path may comprise passive mixers, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 706A of the transmit signalpath may be configured to up-convert input baseband signals based on thesynthesized frequency provided by the synthesizer circuitry 706D togenerate RF output signals for the FEM circuitry 708. The basebandsignals may be provided by the baseband circuitry 704 and may befiltered by filter circuitry 706C. The filter circuitry 706C may includea low-pass filter (LPF), although the scope of the embodiments is notlimited in this respect. In some embodiments, the mixer circuitry 706Aof the receive signal path and the mixer circuitry 706A of the transmitsignal path may include two or more mixers, and may be arranged forquadrature downconversion and/or upconversion, respectively. In someembodiments, the mixer circuitry 706A of the receive signal path and themixer circuitry 706A of the transmit signal path may include two or moremixers and may be arranged for image rejection (e.g., Hartley imagerejection). In some embodiments, the mixer circuitry 706A of the receivesignal path and the mixer circuitry 706A may be arranged for directdownconversion and/or direct upconversion, respectively. In someembodiments, the mixer circuitry 706A of the receive signal path and themixer circuitry 706A of the transmit signal path may be configured forsuper-heterodyne operation.

In some embodiments, the output baseband signals and the input basebandsignals may be analog baseband signals, although the scope of theembodiments is not limited in this respect. In some alternateembodiments, the output baseband signals and the input baseband signalsmay be digital baseband signals. In such embodiments, the RF circuitry706 may include analog-to-digital converter (ADC) and digital-to-analogconverter (DAC) circuitry, and the baseband circuitry 704 may include adigital baseband interface to communicate with the RF circuitry 706.

In some dual-mode embodiments, separate radio IC circuitry may beprovided for processing signals for each spectrum, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 706D may include one ormore of a fractional-N synthesizer and a fractional N/N+1 synthesizer,although the scope of the embodiments is not limited in this respect asother types of frequency synthesizers may be suitable. For example,synthesizer circuitry 706D may include a delta-sigma synthesizer, afrequency multiplier, a synthesizer comprising a phase-locked loop witha frequency divider, other synthesizers and combinations thereof.

The synthesizer circuitry 706D may be configured to synthesize an outputfrequency for use by the mixer circuitry 706A of the RF circuitry 706based on a frequency input and a divider control input. In someembodiments, the synthesizer circuitry 706D may be a fractional N/N+1synthesizer.

In some embodiments, frequency input may be provided by a voltagecontrolled oscillator (VCO), although that is not a requirement. Dividercontrol input may be provided by either the baseband circuitry 704 orthe applications processor 702 depending on the desired outputfrequency. In some embodiments, a divider control input (e.g., N) may bedetermined from a look-up table based on a channel indicated by theapplications processor 702.

The synthesizer circuitry 706D of the RF circuitry 706 may include adivider, a delay-locked loop (DLL), a multiplexer and a phaseaccumulator. In some embodiments, the divider may include a dual modulusdivider (DMD), and the phase accumulator may include a digital phaseaccumulator (DPA). In some embodiments, the DMD may be configured todivide the input signal by either N or N+1 (e.g., based on a carry out)to provide a fractional division ratio. In some example embodiments, theDLL may include a set of cascaded, tunable, delay elements, a phasedetector, a charge pump and a D-type flip-flop. In such embodiments, thedelay elements may be configured to break a VCO period up into Nd equalpackets of phase, where Nd is the number of delay elements in the delayline. In this way, the DLL may provide negative feedback to help ensurethat the total delay through the delay line is one VCO cycle.

In some embodiments, the synthesizer circuitry 706D may be configured togenerate a carrier frequency as the output frequency. In someembodiments, the output frequency may be a multiple of the carrierfrequency (e.g., twice the carrier frequency, four times the carrierfrequency, etc.) and used in conjunction with a quadrature generator anddivider circuitry to generate multiple signals at the carrier frequencywith multiple different phases with respect to each other. In someembodiments, the output frequency may be a LO frequency (fLO). In someembodiments, the RF circuitry 706 may include an IQ/polar converter.

The FEM circuitry 708 may include a receive signal path which mayinclude circuitry configured to operate on RF signals received from oneor more antennas 710, amplify the received signals, and provide theamplified versions of the received signals to the RF circuitry 706 forfurther processing. The FEM circuitry 708 may also include a transmitsignal path which may include circuitry configured to amplify signalsfor transmission provided by the RF circuitry 706 for transmission by atleast one of the one or more antennas 710.

In some embodiments, the FEM circuitry 708 may include a TX/RX switchconfigured to switch between a transmit mode and a receive modeoperation. The FEM circuitry 708 may include a receive signal path and atransmit signal path. The receive signal path of the FEM circuitry 708may include a low-noise amplifier (LNA) to amplify received RF signalsand provide the amplified received RF signals as an output (e.g., to theRF circuitry 706). The transmit signal path of the FEM circuitry 708 mayinclude a power amplifier (PA) configured to amplify input RF signals(e.g., provided by RF circuitry 706), and one or more filters configuredto generate RF signals for subsequent transmission (e.g., by one or moreof the one or more antennas 710.

In some embodiments, the MS device 700 may include additional elementssuch as, for example, memory/storage, a display, a camera, one of moresensors, an input/output (I/O) interface, other elements, andcombinations thereof.

In some embodiments, the MS device 700 may be configured to perform oneor more processes, techniques, and/or methods as described herein, orportions thereof.

FIG. 8 shows a method 800 for using a prioritized timing reference inLTE. The method can be accomplished using various systems, including thesystems shown in FIGS. 1 and 9. In block 802, a UE receives aprioritized list of synchronization sources including GNSS and evolvedNode B (eNB). In block 804, the UE selects a timing reference based atleast in part on a ranking system of the synchronization sources. Inblock 806, the UE synchronizes transmission timing to the timingreference of the synchronization source.

FIG. 9 is a block diagram illustrating components, according to someexample embodiments, able to read instructions from a machine-readableor computer-readable medium (e.g., a machine-readable storage medium)and perform any one or more of the methodologies discussed herein.Specifically, FIG. 9 shows a diagrammatic representation of hardwareresources 900 including one or more processors (or processor cores) 910,one or more memory/storage devices 920, and one or more communicationresources 930, each of which are communicatively coupled via a bus 940.

The processors 910 (e.g., a central processing unit (CPU), a reducedinstruction set computing (RISC) processor, a complex instruction setcomputing (CISC) processor, a graphics processing unit (GPU), a digitalsignal processor (DSP) such as a baseband processor, an applicationspecific integrated circuit (ASIC), a radio-frequency integrated circuit(RFIC), another processor, or any suitable combination thereof) mayinclude, for example, a processor 912 and a processor 914. Thememory/storage devices 920 may include main memory, disk storage, or anysuitable combination thereof.

The communication resources 930 may include interconnection and/ornetwork interface components or other suitable devices to communicatewith one or more peripheral devices 904 and/or one or more databases 906via a network 908. For example, the communication resources 930 mayinclude wired communication components (e.g., for coupling via aUniversal Serial Bus (USB)), cellular communication components, NearField Communication (NFC) components, Bluetooth® components (e.g.,Bluetooth® Low Energy), Wi-Fi® components, and other communicationcomponents.

Instructions 950 may comprise software, a program, an application, anapplet, an app, or other executable code for causing at least any of theprocessors 910 to perform any one or more of the methodologies discussedherein. The instructions 950 may reside, completely or partially, withinat least one of the processors 910 (e.g., within the processor's cachememory), the memory/storage devices 920, or any suitable combinationthereof. Furthermore, any portion of the instructions 950 may betransferred to the hardware resources 900 from any combination of theperipheral devices 904 and/or the databases 906. Accordingly, the memoryof processors 910, the memory/storage devices 920, the peripheraldevices 904, and the databases 906 are examples of computer-readable andmachine-readable media.

Examples

Example 1 is a system for wireless transmissions using a prioritizedtiming reference. The system includes a global navigation satellitesystem (GNSS) receiver; a wireless transceiver configured to communicatewith a first device; and a processor. The processor is designed toreceive a prioritized list of synchronization sources including GNSS andenhanced Node B (eNB); select a timing reference based at least in parton a ranking system of the synchronization sources; and synchronizetransmission timing to the timing reference of the synchronizationsource.

In Example 2, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a prioritized list ofsynchronization sources to receive the prioritized list from an eNB.

In Example 3, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a prioritized list ofsynchronization sources containing a user equipment

In Example 4, the subject matter of Example 1 or any of the Examplesdescribed herein may further include selecting a lower prioritysynchronization source over a higher priority synchronization source,based in part on availability, when selecting the timing reference.

In Example 5, the subject matter of Example 1 or any of the Examplesdescribed herein may further include propagating the timing informationfor devices without GNSS synchronization.

In Example 6, the subject matter of Example 1 or any of the Examplesdescribed herein may further include an in-coverage device using GNSSbased on an enhanced Node B (eNB) priority message.

In Example 7, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a transmission timing whichincludes transmissions that are frame mapped to coordinated universaltime (UTC).

In Example 8, the subject matter of Example 7 or any of the Examplesdescribed herein may further include a transmission timing whichincludes a separate offset indicator for timing below one millisecond.

In Example 9, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a prioritized list ofsynchronization sources which includes data indicating a level ofsynchronization in frequency, phase, or time.

In Example 10, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a prioritized list ofsynchronization sources which includes data indicating the signaling ofthe timing offset in a granularity of less that cyclic prefix durationrelative to global coordinated universal time (UTC).

In Example 11, the subject matter of Example 1 or any of the Examplesdescribed herein may further include the timing reference between anetwork system timing, a GNSS system timing, and proximity services(ProSe) system timing which are related to a common global timingreference.

In Example 12, the subject matter of Example 11 or any of the Examplesdescribed herein may further include an alignment of resourceallocations within and out of network coverage that are aligned to theglobal timing reference.

In Example 13, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a processor designed to receive theGNSS assistance information broadcasted by the eNB in system informationblocks.

In Example 14, the subject matter of Example 1 or any of the Examplesdescribed herein may further include the GNSS assistance information inlong term evolution positioning protocol (LPP) to be reused.

In Example 15, the subject matter of Example 14 or any of the Examplesdescribed herein may further include the GNSS-ReferenceTime data elementreused for a relationship between GNSS system time and networkair-interface timing of the eNB transmission in a reference cell.

In Example 16, the subject matter of Example 14 or any of the Examplesdescribed herein may further include the GNSS-ReferenceLocation dataelement reused to provide knowledge of a location to improve GNSSreceiver performance.

In Example 17, the subject matter of Example 14 or any of the Examplesdescribed herein may further include the GNSS-GenericAssistDataElementdata element reused to improve GNSS performance.

In Example 18, the subject matter of Example 1 or any of the Examplesdescribed herein may further include the processor designed to receivepropagation of synchronization information based on a type of thesynchronization source, based on transmission of the synchronizationsignal or synchronization channel.

In Example 19, the subject matter of Example 1 or any of the Examplesdescribed herein may further include the processor designed to receive asynchronization signal or synchronization channel which carriesinformation about a type of the synchronization source.

In Example 20, the subject matter of Example 1 or any of the Examplesdescribed herein may further include the processor designed to receive adedicated synchronization resource which is allocated to propagatesynchronization based on type of synchronization source.

In Example 21, the subject matter of Example 1 or any of the Examplesdescribed herein may further include a timing reference which includesselecting a combination of synchronization sources.

In Example 22, the subject matter of Example 21 or any of the Examplesdescribed herein may further include the combination of synchronizationsources selected from GNSS, eNB or user equipment (UE).

In Example 23, the subject matter of Example 1 or any of the Examplesdescribed herein may further include eNB and GNSS timing aligned andassociated with common resource allocation, unambiguously defining aphysical structure of resource pool configuration for data and control,once a UE acquires timing information.

Example 24 is an apparatus of a user equipment (UE). The apparatusincludes a global navigation satellite system (GNSS) interface, awireless cellular interface, and a processor. The GNSS interface isattached to a GNSS receiver. The wireless cellular interface is designedto communicate with a peer UE. The processor is attached to the GNSSinterface and wireless cellular interface, and is designed to determineavailable synchronization sources, select a GNSS synchronization sourcebased in part on a priority rule, and transmit an indication of the GNSSsynchronization source to the peer UE.

In Example 25, the subject matter of Example 24 or any of the Examplesdescribed herein may further include the GNSS synchronization sourcetransmitted via a primary sidelink synchronization signal (PSSS).

In Example 26, the subject matter of Example 24 or any of the Examplesdescribed herein may further include the GNSS synchronization sourcetransmitted via a secondary sidelink synchronization signal (SSSS).

In Example 27, the subject matter of Example 24 or any of the Examplesdescribed herein may further include the GNSS synchronization sourcetransmitted via a physical sidelink broadcast channel PSBCH payload.

In Example 28, the subject matter of Example 24 or any of the Examplesdescribed herein may further include the GNSS synchronization source tobe determined by an implicit indication.

Example 29 is an apparatus of an enhanced node B (eNB). The apparatusincludes a processor designed to transmit assistance informationindicating a GNSS synchronization source, and establish phase,frequency, or time synchronization with the device.

In Example 30, the subject matter of Example 29 or any of the Examplesdescribed herein may further include the apparatus containing a globalnavigation satellite system (GNSS) receiver, and a wireless transceiverdesigned to communicate with the device.

In Example 31, the subject matter of Example 29 or any of the Examplesdescribed herein may further include the processor designed to enablethe apparatus to act as a synchronization source for the device in anin-coverage scenario.

In Example 32, the subject matter of Example 29 or any of the Examplesdescribed herein may further include the processor designed to enablethe apparatus to act as a synchronization source for the device thatlacks a GNSS receiver.

In Example 33, the subject matter of Example 29 or any of the Examplesdescribed herein may further include the processor designed tocommunicate with the device without acting as a synchronization sourcefor the device in an in-coverage scenario.

Example 34 is a computer program product. The computer program productincludes a computer-readable storage medium storing program code. Thecomputer-readable storage medium storing program code causes one or moreprocessors to perform a method. The method includes determiningavailable synchronization sources; selecting, based in part on apriority rule, a synchronization source from a set of synchronizationsources for proximity services communication with a first user equipment(UE); communicating assistance information containing the selectedsynchronization source to the UE; establishing a common timing based onthe selected synchronization source reference; and propagating thecommon timing to a second UE for which the selected synchronizationsource is unavailable.

In Example 35, the subject matter of Example 34 or any of the Examplesdescribed herein may further include global navigation satellite system(GNSS) and enhanced node B (eNB) synchronization in the synchronizationsources.

In Example 36, the subject matter of Example 34 or any of the Examplesdescribed herein may further include the synchronization sourcescontaining a combination of a global navigation satellite system (GNSS)and enhanced node B (eNB) synchronization.

In Example 37, the subject matter of Example 34 or any of the Examplesdescribed herein may further include communicating the assistanceinformation by transmitting the assistance information over a sidelinkchannel.

In Example 38, the subject matter of Example 34 or any of the Examplesdescribed herein may further include the priority rule based on whetherthe first UE is in-coverage.

In Example 39, the subject matter of Example 38 or any of the Examplesdescribed herein may further include the priority rule to be GNSS beforean eNB signal before a UE signal.

In Example 40, the subject matter of Example 38 or any of the Examplesdescribed herein may further include the priority rule to be an enhancednode B (eNB) signal before GNSS before a UE signal.

In Example 41, the subject matter of Example 34 or any of the Examplesdescribed herein may further include the priority rule based on whetherthe first UE is out of coverage.

In Example 42, the subject matter of Example 41 or any of the Examplesdescribed herein may further include priority rule based on GNSS beforea UE signal based on GNSS before a UE signal based on internalsynchronization signal.

In Example 43, the subject matter of Example 41 or any of the Examplesdescribed herein may further include the priority rule containing a UEsignal based on eNB synchronization before a UE signal based on GNSSsynchronization before a UE signal based on internal synchronizationsignal.

Example 44 is an apparatus for synchronization in long term evolution(LTE). The apparatus includes a method for determining availablesynchronization sources; a method for selecting, based in part on apriority rule, a synchronization source from a set of synchronizationsources for proximity services communication with a first user equipment(UE); a method for communicating assistance information comprising theselected synchronization source to the UE; a method for establishing acommon timing based on the selected synchronization source reference;and a method for propagating the common timing to a second UE for whichthe selected synchronization source is unavailable.

In Example 45, the subject matter of Example 44 or any of the Examplesdescribed herein may further include the synchronization sourcescontaining global navigation satellite system (GNSS) and enhanced node B(eNB) synchronization.

In Example 46, the subject matter of Example 44 or any of the Examplesdescribed herein may further include the synchronization sourcescontaining a combination of a global navigation satellite system (GNSS)and enhanced node B (eNB) synchronization.

In Example 47, the subject matter of Example 44 or any of the Examplesdescribed herein may further include a method for communicating theassistance information and for transmitting the assistance informationover a sidelink channel.

Example 48 is a method of synchronization in long term evolution (LTE).The LTE includes determining available synchronization sources;selecting, based in part on a priority rule, a synchronization sourcefrom a set of synchronization sources for proximity servicescommunication with a first user equipment (UE); communicating assistanceinformation containing the selected synchronization source to the UE;establishing a common timing based on the selected synchronizationsource reference; and propagating the common timing to a second UE forwhich the selected synchronization source is unavailable.

In Example 49, the subject matter of Example 48 or any of the Examplesdescribed herein may further include the synchronization sources withglobal navigation satellite system (GNSS) and enhanced node B (eNB)synchronization.

In Example 50, the subject matter of Example 48 or any of the Examplesdescribed herein may further include the synchronization sources with acombination of a global navigation satellite system (GNSS) and enhancednode B (eNB) synchronization.

Example 51 is a method for wireless transmissions using a prioritizedtiming reference. The method includes receiving a prioritized list ofsynchronization sources including a GNSS and an enhanced Node B (eNB);selecting a timing reference based in part on a ranking system of thesynchronization sources; and synchronizing transmission timing to thetiming reference of the synchronization source.

In Example 52, the subject matter of Example 51 or any of the Examplesdescribed herein may further include receiving a prioritized list ofsynchronization sources and a prioritized list from an eNB.

In Example 53, the subject matter of Example 51 or any of the Examplesdescribed herein may further include a prioritized list ofsynchronization sources containing a UE.

In Example 54, the subject matter of Example 51 or any of the Examplesdescribed herein may further include a timing reference containingselecting a lower priority synchronization source over a higher prioritysynchronization source based in part on availability.

Example 55 is a method for wireless transmissions using a prioritizedtiming reference. The method includes transmitting assistanceinformation indicating a GNSS synchronization source; and establishingphase, frequency, or time synchronization information for delivery to adevice in communication with an eNB.

In Example 56, the subject matter of Example 55 or any of the Examplesdescribed herein may further include acting as a synchronization sourcefor the device in an in-coverage scenario.

In Example 57, the subject matter of Example 55 or any of the Examplesdescribed herein may further include acting as a synchronization sourcefor the device that lacks a GNSS receiver.

In Example 58, the subject matter of Example 55 or any of the Examplesdescribed herein may further include communicating with the devicewithout acting as a synchronization source for the device in anin-coverage scenario.

Example 59 is an apparatus containing a procedure to perform a method asidentified in any of Examples 48-58.

Example 60 is a machine-readable storage including machine-readableinstructions, which, when executed, implement a method or realize anapparatus as identified in any of Examples 48-58.

Example 61 is a machine-readable medium including code, which, whenexecuted, causes a machine to perform the method of any one of Examples48-58.

Embodiments and implementations of the systems and methods describedherein may include various operations, which may be embodied inmachine-executable instructions to be executed by a computer system. Acomputer system may include one or more general-purpose orspecial-purpose computers (or other electronic devices). The computersystem may include hardware components that include specific logic forperforming the operations or may include a combination of hardware,software, and/or firmware.

Computer systems and the computers in a computer system may be connectedvia a network. Suitable networks for configuration and/or use asdescribed herein include one or more local area networks, wide areanetworks, metropolitan area networks, and/or Internet or IP networks,such as the World Wide Web, a private Internet, a secure Internet, avalue-added network, a virtual private network, an extranet, anintranet, or even stand-alone machines which communicate with othermachines by physical transport of media. In particular, a suitablenetwork may be formed from parts or entireties of two or more othernetworks, including networks using disparate hardware and networkcommunication technologies.

One suitable network includes a server and one or more clients; othersuitable networks may contain other combinations of servers, clients,and/or peer-to-peer nodes, and a given computer system may function bothas a client and as a server. Each network includes at least twocomputers or computer systems, such as the server and/or clients. Acomputer system may include a workstation, laptop computer,disconnectable mobile computer, server, mainframe, cluster, so-called“network computer” or “thin client,” tablet, smart phone, personaldigital assistant or other hand-held computing device, “smart” consumerelectronics device or appliance, medical device, or a combinationthereof.

Suitable networks may include communications or networking software,such as the software available from Novell®, Microsoft®, and othervendors, and may operate using TCP/IP, SPX, IPX, and other protocolsover twisted pair, coaxial, or optical fiber cables, telephone lines,radio waves, satellites, microwave relays, modulated AC power lines,physical media transfer, and/or other data transmission “wires” known tothose of skill in the art. The network may encompass smaller networksand/or be connectable to other networks through a gateway or similarmechanism.

Various techniques, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as floppy diskettes, CD-ROMs, hard drives, magnetic or opticalcards, solid-state memory devices, a nontransitory computer-readablestorage medium, or any other machine-readable storage medium wherein,when the program code is loaded into and executed by a machine, such asa computer, the machine becomes an apparatus for practicing the varioustechniques. In the case of program code execution on programmablecomputers, the computing device may include a processor, a storagemedium readable by the processor (including volatile and nonvolatilememory and/or storage elements), at least one input device, and at leastone output device. The volatile and nonvolatile memory and/or storageelements may be a RAM, an EPROM, a flash drive, an optical drive, amagnetic hard drive, or other medium for storing electronic data. TheeNB (or other base station) and UE (or other mobile station) may alsoinclude a transceiver component, a counter component, a processingcomponent, and/or a clock component or timer component. One or moreprograms that may implement or utilize the various techniques describedherein may use an application programming interface (API), reusablecontrols, and the like. Such programs may be implemented in a high-levelprocedural or an object-oriented programming language to communicatewith a computer system. However, the program(s) may be implemented inassembly or machine language, if desired. In any case, the language maybe a compiled or interpreted language, and combined with hardwareimplementations.

Each computer system includes one or more processors and/or memory;computer systems may also include various input devices and/or outputdevices. The processor may include a general purpose device, such as anIntel®, AMD®, or other “off-the-shelf” microprocessor. The processor mayinclude a special purpose processing device, such as ASIC, SoC, SiP,FPGA, PAL, PLA, FPLA, PLD, or other customized or programmable device.The memory may include static RAM, dynamic RAM, flash memory, one ormore flip-flops, ROM, CD-ROM, DVD, disk, tape, or magnetic, optical, orother computer storage medium. The input device(s) may include akeyboard, mouse, touch screen, light pen, tablet, microphone, sensor, orother hardware with accompanying firmware and/or software. The outputdevice(s) may include a monitor or other display, printer, speech ortext synthesizer, switch, signal line, or other hardware withaccompanying firmware and/or software.

It should be understood that many of the functional units described inthis specification may be implemented as one or more components, whichis a term used to more particularly emphasize their implementationindependence. For example, a component may be implemented as a hardwarecircuit comprising custom very large scale integration (VLSI) circuitsor gate arrays, or off-the-shelf semiconductors such as logic chips,transistors, or other discrete components. A component may also beimplemented in programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices, orthe like.

Components may also be implemented in software for execution by varioustypes of processors. An identified component of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object, aprocedure, or a function. Nevertheless, the executables of an identifiedcomponent need not be physically located together, but may comprisedisparate instructions stored in different locations that, when joinedlogically together, comprise the component and achieve the statedpurpose for the component.

Indeed, a component of executable code may be a single instruction, ormany instructions, and may even be distributed over several differentcode segments, among different programs, and across several memorydevices. Similarly, operational data may be identified and illustratedherein within components, and may be embodied in any suitable form andorganized within any suitable type of data structure. The operationaldata may be collected as a single data set, or may be distributed overdifferent locations including over different storage devices, and mayexist, at least partially, merely as electronic signals on a system ornetwork. The components may be passive or active, including agentsoperable to perform desired functions.

Several aspects of the embodiments described will be illustrated assoftware modules or components. As used herein, a software module orcomponent may include any type of computer instruction orcomputer-executable code located within a memory device. A softwaremodule may, for instance, include one or more physical or logical blocksof computer instructions, which may be organized as a routine, program,object, component, data structure, etc., that perform one or more tasksor implement particular data types. It is appreciated that a softwaremodule may be implemented in hardware and/or firmware instead of or inaddition to software. One or more of the functional modules describedherein may be separated into sub-modules and/or combined into a singleor smaller number of modules.

In certain embodiments, a particular software module may includedisparate instructions stored in different locations of a memory device,different memory devices, or different computers, which togetherimplement the described functionality of the module. Indeed, a modulemay include a single instruction or many instructions, and may bedistributed over several different code segments, among differentprograms, and across several memory devices. Some embodiments may bepracticed in a distributed computing environment where tasks areperformed by a remote processing device linked through a communicationsnetwork. In a distributed computing environment, software modules may belocated in local and/or remote memory storage devices. In addition, databeing tied or rendered together in a database record may be resident inthe same memory device, or across several memory devices, and may belinked together in fields of a record in a database across a network.

Reference throughout this specification to “an example” means that aparticular feature, structure, or characteristic described in connectionwith the example is included in at least one embodiment of the presentembodiments. Thus, appearances of the phrase “in an example” in variousplaces throughout this specification are not necessarily all referringto the same embodiment.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based onits presentation in a common group without indications to the contrary.In addition, various embodiments and examples may be referred to hereinalong with alternatives for the various components thereof. It isunderstood that such embodiments, examples, and alternatives are not tobe construed as de facto equivalents of one another, but are to beconsidered as separate and autonomous representations.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided, such asexamples of materials, frequencies, sizes, lengths, widths, shapes,etc., to provide a thorough understanding of embodiments presented. Oneskilled in the relevant art will recognize, however, that the variousembodiments may be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures, materials, or operations are not shownor described in detail to avoid obscuring aspects of the variousembodiments.

It should be recognized that the systems described herein includedescriptions of specific embodiments. These embodiments can be combinedinto single systems, partially combined into other systems, split intomultiple systems or divided or combined in other ways. In addition, itis contemplated that parameters/attributes/aspects/etc. of oneembodiment can be used in another embodiment. Theparameters/attributes/aspects/etc. are merely described in one or moreembodiments for clarity, and it is recognized that theparameters/attributes/aspects/etc. can be combined with or substitutedfor parameters/attributes/aspects/etc. of another embodiment unlessspecifically disclaimed herein.

Although the foregoing has been described in some detail for purposes ofclarity, it will be apparent that certain changes and modifications maybe made without departing from the principles thereof. It should benoted that there are many alternative ways of implementing both theprocesses and apparatuses described herein. Accordingly, the presentembodiments are to be considered illustrative and not restrictive, andthe disclosure is not to be limited to the details given herein, but maybe modified within the scope and equivalents of the appended claims.

Those having skill in the art will appreciate that many changes may bemade to the details of the above-described embodiments without departingfrom the underlying principles. The scope of the present disclosureshould, therefore, be determined only by the following claims.

1-16. (canceled)
 17. An apparatus of a user equipment (UE), comprising:a global navigation satellite system (GNSS) interface coupled to a GNSSreceiver; a wireless cellular interface configured to communicate with apeer UE; a processor coupled to the GNSS interface and wireless cellularinterface, the processor configured to: determine availablesynchronization sources; select a GNSS synchronization source based atleast in part on a priority rule; and transmit an indication of the GNSSsynchronization source to the peer UE.
 18. The apparatus of claim 17,wherein indication of the GNSS synchronization source is transmitted viaa primary sidelink synchronization signal (PSSS), via a secondarysidelink synchronization signal (SSSS) or via a physical sidelinkbroadcast channel (PSBCH) payload.
 19. The apparatus of claim 17,wherein indication of the GNSS synchronization source is determined byan implicit indication.
 20. An apparatus of an evolved node B (eNB)comprising: a processor configured to: generate assistance informationindicating a GNSS synchronization source; and establish phase, frequencyor time synchronization information for delivery to a device incommunication with the eNB.
 21. The apparatus of claim 20, wherein theapparatus further comprises: a global navigation satellite system (GNSS)receiver; and a wireless transceiver configured to communicate with thedevice.
 22. The apparatus of claim 20, wherein the processor is furtherconfigured to enable the apparatus to act as a synchronization sourcefor the device in an in-coverage scenario.
 23. The apparatus of claim20, wherein the processor is further configured to enable the apparatusto act as a synchronization source for the device that lacks a GNSSreceiver.
 24. The apparatus of claim 20, wherein the processor isfurther configured to communicate with the device without acting as asynchronization source for the device in an in-coverage scenario.
 25. Acomputer program product comprising a computer-readable storage mediumstoring program code for causing one or more processors to perform amethod, the method comprising: determining available synchronizationsources; selecting, based at least in part on a priority rule, asynchronization source from a set of synchronization sources forproximity services communication with a first user equipment (UE);communicate assistance information comprising the selectedsynchronization source to the UE; establishing a common timing based onthe selected synchronization source reference; propagating the commontiming to a second UE for which the selected synchronization source isunavailable.
 26. The computer program product of claim 25, wherein thesynchronization sources include global navigation satellite system(GNSS) and evolved node B (eNB) synchronization.
 27. The computerprogram product of claim 25, wherein to communicate the assistanceinformation further comprises transmitting the assistance informationover a sidelink channel.
 28. The computer program product of claim 25,wherein the priority rule based on whether the first UE is in-coverage.